STOCK OPTION PLANS (Details) (USD $)	3 Months Ended		6 Months Ended											3 Months Ended		6 Months Ended		3 Months Ended		6 Months Ended		3 Months Ended			6 Months Ended		0 Months Ended	6 Months Ended
	Jun. 30, 2013	May 31, 2012	Jun. 30, 2013	May 31, 2012	Jun. 30, 2013 $ 0 to $1.00 [Member]	Jun. 30, 2013 $ 1.01 to $2.00 [Member]	Jun. 30, 2013 $ 2.01 to $3.00 [Member]	Jun. 30, 2013 $ 3.01 to $4.00 [Member]	Jun. 30, 2013 $ 4.01 to $5.00 [Member]	Jun. 30, 2013 $ 5.01 to $6.00 [Member]	Jun. 30, 2013 $ 6.01 to $7.00 [Member]	Jun. 30, 2013 $ 7.01 to $8.00 [Member]	Jun. 30, 2013 $ 8.01 to $964.24 [Member]	Jun. 30, 2013 Research and Development Expense [Member]	May 31, 2012 Research and Development Expense [Member]	Jun. 30, 2013 Research and Development Expense [Member]	May 31, 2012 Research and Development Expense [Member]	Jun. 30, 2013 General and Administrative Expense [Member]	May 31, 2012 General and Administrative Expense [Member]	Jun. 30, 2013 General and Administrative Expense [Member]	May 31, 2012 General and Administrative Expense [Member]	Jun. 30, 2013 Stock Options [Member]	Mar. 31, 2013 Stock Options [Member]	May 31, 2012 Stock Options [Member]	Jun. 30, 2013 Stock Options [Member]	May 31, 2012 Stock Options [Member]	Jul. 23, 2013 2013 Plan Amendment [Member]	Jun. 30, 2013 2010 Equity Incentive Plan [Member] Age	Jun. 30, 2013 2010 Equity Incentive Plan [Member] Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Increase in share reserve available for issuance (in shares)																											3,000,000
Aggregate share reserve available for issuance (in shares)																											11,900,000
Exercises of stock options			$ 7,000																			$ 0			$ 7,000
Exercise of stock options (in shares)																						0	8,000		8,014
Assumptions of Black-Scholes option pricing model for stock-based compensation expense [Abstract]
Risk-free interest rate (in hundredths)			0.92%																			0.92%		0.89%
Expected life of stock option			5 years																			5 years		5 years
Annual volatility (in hundredths)			78.00%																			77.83%		124.00%
Dividend rate (in hundredths)			0.00%																			0.00%		0.00%
Option shares [Roll Forward]
Outstanding, beginning of period (in shares)																						7,885,000	7,791,000		7,791,000
Granted (in shares)																						478,000	130,000
Exercised (in shares)																						0	(8,000)		(8,014)
Canceled (in shares)																						(27,000)	(28,000)
Outstanding, end of period (in shares)																						8,336,000	7,885,000		8,336,000
Weighted-average exercise price [Roll Forward]
Outstanding, beginning of period (in dollars per share)																						$ 5.76	$ 5.79		$ 5.79
Granted (in dollars per share)																						$ 6.58	$ 5.39
Exercised (in dollars per share)																						$ 0	$ 0.85
Canceled (in dollars per share)																						$ 20.70	$ 13.94
Outstanding, end of period (in dollars per share)																						$ 5.76	$ 5.76		$ 5.76
Exercisable [Roll Forward]
Outstanding, beginning of period (in shares)																						4,031,000	3,494,000		3,494,000
Granted (in shares)																						0	0
Exercised (in shares)																						0	0
Canceled (in shares)																						0	0
Outstanding, end of period (in shares)																						4,525,000	4,031,000		4,525,000
Weighted-average fair value of options granted [Roll Forward]
Outstanding, beginning of period (in dollars per share)																						$ 3.47	$ 3.48		$ 3.48
Granted (in dollars per share)																						$ 4.01	$ 3.04
Exercised (in dollars per share)																						$ 0	$ 0.62
Canceled (in dollars per share)																						$ 4.73	$ 4.25
Outstanding, end of period (in dollars per share)																						$ 3.55	$ 3.47		$ 3.55
Weighted-average intrinsic values of stock options [Abstract]
Intrinsic values of options outstanding and expected to vest																						39,779,000		20,400,000
Number of options outstanding and expected to vest (in shares)																						8,336,000		5,800,000
Intrinsic values of options exercisable																									24,111,000	1,600,000
Number of options exercisable (in shares)																									4,525,000	3,700,000
Number of shares available for grant (in shares)																													1,400,000
Percentage of accelerated vesting of unvested stock options allowed as per amendments (in hundredths)																												50.00%
Minimum age of employee for extension of termination date																												62
Minimum years of continuous service prior to retirement																												5 years
Minimum number of days of continuous service in case of death or permanent disability																												90 days
Extension of termination date																												18 months
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Employee and consultant stock-based compensation expense	1,846,000	1,198,000	3,597,000	2,349,000										380,000	248,000	742,000	510,000	1,466,000	950,000	2,855,000	1,839,000
Options outstanding under stock option plans [Abstract]
Range of exercise prices, minimum (in dollars per share)					$ 0	$ 1.01	$ 2.01	$ 3.01	$ 4.01	$ 5.01	$ 6.01	$ 7.01	$ 8.01
Range of exercise prices, maximum (in dollars per share)					$ 1.00	$ 2.00	$ 3.00	$ 4.00	$ 5.00	$ 6.00	$ 7.00	$ 8.00	$ 964.24
Options outstanding, number of options outstanding and expected to vest (in shares)	8,336,000		8,336,000		1,000	79,000	1,353,000	1,764,000	310,000	4,083,000	523,000	182,000	41,000
Options outstanding, weighted-average remaining contractual life			7 years 10 months 17 days		5 years 9 months 18 days	5 years 11 months 19 days	5 years 4 months 20 days	7 years 4 months 24 days	8 years 4 months 28 days	8 years 8 months 19 days	9 years 2 months 16 days	9 years 5 months 8 days	2 years 4 months 24 days
Options outstanding, weighted-average exercise price (in dollars per share)	$ 5.76		$ 5.76		$ 0.85	$ 1.78	$ 2.66	$ 3.50	$ 4.79	$ 5.29	$ 6.46	$ 7.69	$ 251.19
Options exercisable, number of options exercisable (in shares)	4,525,000		4,525,000		1,000	76,000	1,168,000	1,439,000	124,000	1,553,000	100,000	23,000	41,000
Options exercisable, weighted average exercise price (in dollars per share)	$ 6.19		$ 6.19		$ 0.85	$ 1.77	$ 2.62	$ 3.52	$ 4.74	$ 5.25	$ 6.49	$ 7.75	$ 251.19
Total unrecognized compensation cost	$ 13,800,000		$ 13,800,000
Weighted-average period over which compensation cost expected to be recognized			3 years